1. Field of the Invention
The present invention relates to a view angle controllable display device (hereinafter simply referred to as “display device”) capable of changing the viewable angle range, and a terminal having the same.
2. Description of Related Art
With the recent development of technology, liquid crystal display devices viewable in wide angle range have been used practically. On the other hand, portable information terminals in which liquid crystal displays (LCD) are mounted have also been used widely. For such a portable information terminal, when obtained information is shared with someone, it is desirable that the display be viewable at wide angle. On the other hand, when it is used as a portable information terminal, the user may reluctant to be looked into the display by others. Therefore, the view angle range must be wide and narrow, depending on the used state. Japanese Patent Application Laid-Open No. 9-105958 (Patent Document 1) discloses a display device satisfying the above requirements.
FIGS. 14 and 15 show a display device disclosed in Patent Document 1. FIG. 14 is a cross-sectional view of a compensating panel, and FIG. 15 is an exploded perspective view of the display device. Hereinafter, description will be given based on these drawings.
As shown in FIG. 14, a compensating panel 101a is so configured that transparent electrode layers 104 and 105 are formed on opposite surfaces of a pair of glass substrates 102 and 103, and orientation films 106 and 107 made of polyimide or vinyl alcohol are formed thereon. Between the glass substrates 102 and 103, a liquid crystal layer 108 made of nematic liquid crystal or the like is formed. A compensating panel 101b has the same configuration as that of the compensating panel 101a. 
As shown in FIG. 15, the compensating panels 101a and 101b constitute a display device 138, combined with a display panel 118 and polarizing plates 109 and 110. The polarizing plates 109 and 110 are arranged on the both sides of the display panel 118, and the compensating panels 101a and 101b are arranged between the display panel 118 and the polarizing plate 109.
Although not shown, the display panel 118 is so configured that a liquid crystal layer made of nematic liquid crystal or the like is filled in the space between a pair of glass substrates in which a transparent electrode layer and an orientation film are formed on the surfaces thereof, and it is sealed with a sealing member made of resin or the like. Each surface of the orientation film of the display panel 118 is rubbing-processed beforehand such that liquid crystal molecules are twist-oriented at about 90°. The rubbing direction of the orientation film on the glass substrate on the upper side is shown by the arrow 119 direction. The rubbing direction of the orientation film on the glass substrate on the lower side is shown by the arrow 120 direction which is orthogonal to the arrow 119.
In the compensating panels 101a and 101b, liquid crystal molecules are oriented so as to be parallel to the surfaces of the glass substrates 102 and 103 in the liquid crystal layers 108 when a voltage is not applied. The orientation directions 124 and 125, which are parallel thereto, are oriented so as to be parallel and orthogonal to the rubbing direction of the pair of glass substrates of the display panel 118, respectively. The compensating panels 101a and 101b are stacked in this manner.
The transparent axis 121 of the polarizing plate 109 and the transparent axis 122 of the polarizing plate 110 are arranged to be orthogonal to each other, and the transparent axis 122 of the polarizing plate 110 and the rubbing direction 120 of the orientation film on the lower side of the display panel 118 are parallel to each other. Therefore, it is in a normally white mode in which the display device 138 transmits light so as to perform white display when a voltage is not applied to the liquid crystal layer of the display panel 118.
When a voltage is not applied to the compensating panels 101a and 101b, the oscillating direction of light passed through the display panel 118 becomes parallel or vertical to the orientation directions 124 and 125 of the liquid crystal molecules of the compensating panels 101a and 101b. Therefore, when the display device 138 is viewed from the immediately above direction, no phase difference is caused even though light passed through the display panel 118 passes the compensating panels 101a and 101b. Therefore, an image which is nothing different from that of a conventional display device can be recognized.
In such a case, the phase shifts as the display device is viewed more obliquely, compared with a conventional display device. However, by optimizing the refractive index anisotropy an of the liquid crystal material of the compensating panels 101a and 101b or the cell gap between the compensating panels 101a and 101b, it is possible to display an image without involving a significant difference from the view angle characteristics of the conventional display device.
On the other hand, in a state where a voltage is applied to the compensating panels 101a and 101b, the liquid crystal molecules inside the liquid crystal layers 108 of the compensating panels 101a and 101b are arranged vertically to the glass substrates 102 and 103. Therefore, when the display device 138 is viewed from the right above, there is no change in the display characteristics. However, when the display device is viewed obliquely from any direction, a phase delay is caused when light passed through the display panel 118 passes through the compensating panels 101a and 101b. Therefore, it is possible to prevent an image from being recognized as an image.
In this way, by applying or not applying a voltage to the compensating panels 101a and 101b, it is possible to change the orientation state of the liquid crystal layer 108 to thereby change the view angle characteristics of the display device 138.
However, the display device disclosed in Patent Document 1 requires at least two compensating panels having a pair of glass substrates, which involves a problem that the device becomes very thick and heavy.